The file is a Readme with instructions how to request the actual firmware, since this is an alpha release (very buggy experimental firmware). Don't bother with it for now unless you are interested in testing, rather than using, the router.
Sorry, I guess I should make sure I have my glasses on before I reply...especially on the smaller phone screen. I mistook this for one of the alpha versions that has a download that is only a text file, not even for same router.